What are some GREAT abdominal exercises?
I have been doing the same variety of ab exercises for a while now and I dont feel challenged anymore which means its not very effective anymore.
Anyone have any tricks or tips to share?
I have a flat stomach but i want all over definition, so both lower and upper ab exercises are welcome!
Thanks in advance

If you’re properly contracting your abs, you shouldn’t be able to do more than about 3 sets of 15 crunches.
There are no upper or lower abs. "Abs" are really just one muscle group. The reason there are splits is because of tendons that run across the abs, and the muscle group pushing through the tendons.